OSCEOLA COUNTY, Fla. -- Family members can't believe a 17-year-old boy is accused of attacking and killing a 99-year-old woman in her Poinciana home and police say they don't know what the motive was.

Moise Opont, 17, lives three doors down and across the street from 99-year-old Edith Mecalla's house. A tip lead investigators to the house of the troubled teenager, who has been arrested twice before for crimes that never came close to what happened to the 99-year-old.

Mecalla was full of life, laughter and she was light on her feet. Her granddaughter told Eyewitness News she loved to dance. That's one of the things that kept her healthy for so long. Her family is heartbroken over the way she was awakened two nights ago, sexually assaulted and struck until she died.

Investigators said Edith's 77-year-old daughter Hazel got a good look at the attacker while he was still in the house, until he struck her with something and she became disoriented.

Neither woman knew Opont, but the daughter's description was so detailed, once investigators got a tip that Opont was their guy, they noticed the strong resemblance to the composite sketch and said the teenager later implicated himself.

Opont's father, who is a local minister, told Eyewitness News his son is a student at Poinciana High School and said investigators have shared very little information with him, but he would not talk about the charges against his son.

Opont is 37 days away from his 18th birthday, a birthday he'll almost definitely spend in custody. By the time prosecutors decide whether to charge him as an adult, he probably will be an adult.